In fuel cell systems, for example, in order to ensure security, it is necessary to monitor whether or not hydrogen gas (fuel gas) leaks from gas piping or a fuel cell. Meanwhile, while power is being generated in the fuel cell systems, hydrogen gas is being consumed in the fuel cell, so whether a gas leakage occurs or not needs to be determined by taking the amount of hydrogen gas consumption into consideration.
In the fuel cell system described in Patent Document 1 indicated below, whether a gas leakage occurs or not is determined based on an amount of gas difference which is obtained by subtracting, from the flow rate of hydrogen gas supplied to a gas supply flow path, an amount of hydrogen gas consumed in a fuel cell and an amount of variation of hydrogen gas flowing into a leakage-check flow path.
Patent Document 1: Japanese laid-open patent publication No. 2006-179469